Method of minimizing ester formation in hydrocarbon synthesis



Jan. 9, 1951 c. H. woRsHAM METHOD 0E MINIMIZING ESTER FORMATION 1N EYDRocAREoN SYNTHESIS Filed Feb. 2o, 1948 r o L a e V Q. 5 m fm w F.. s 8 7F. ha C b5 dbd/MGvucr D. e5

Patented Jan. 9, 195,1

METHOD OF MINIMIZIN G ESTER FORMA- TION IN HYDROCARBON SYNTHESIS Charles H. Worsham, Fanwood, N. J., assignor to 4Standard Oil Development Company, a corporation of Delaware Application February 20, 1948, Serial No. 9,644

. 5. Claims. (Cl.`260-449.6)

This invention relates to the synthesis of hydrocarbons and oxygenated hydrocarbons from carbon monoxide and hydrogen. More particularly, this invention relates to a process for increasing the amount of acids and alcohols-Which maybe recovered from such synthesis-process.

It is well known inthe art that mixtures of carbon monoxide and lhydrogen when brought into intimate contact with suitable catalysts under suitable reaction conditions are converted into hydrocarbons and oxygenated hydrocarbons. It also known that the nature of the products are in general a function of the reaction conditions, such as temperature, pressure, contact time, feed gas ratio, and the nature of the catalyst. Thus it has been established that in general increasing the pressure favors the formation of oxygenated organic products and also that alkali metal promoted iron type catalysts favor oxygenated conversion products as against the cobalt-type catalysts. y

These oxygenated compounds which appear in the product of the catalytic reaction between CO and H2, and which may in accordance With the reaction conditions, amount to as much as 50% of the liquid yield, and include alcohols, aldehydes, ketones, acids, and esters, are found distributed between the product Water and oil layers of the rst product condensate of the conventional fluid or xed bed hydrocarbon synthesis. These oxygenated organic products have a considerable commercial value and their recovery` by eht invention to provide an improved process for increasing the yield of alcohols and acids from the catalytic synthesis of hydrocarbons and oxyeconomic methods may improve substantially the economic aspects of the hydrocarbon synthesis. Particularly the lower alcohols, such as .ethyl and propyl are of the highest technical and commercial importance and interest, as are also the lowerV molecular weight carboxylic acids, as acetic and propionic. Of somewhat less importance are the esters and the carbonyl compounds and the higher molecular weight products, which appear in smaller quantities. l

In order to increase the economic attractiveness of the hydrocarbon synthesis process as a means for` manufacturing valuable low molecular weight alcohols and acids, it is most desirable to produce these at the expense of the less valuable oxygenated products, such as esters. It is true that esters, once obtained and isolated, may be converted subsequently into alcohols and acids by hydrolysis or saponication, but this would add two further steps to the process with accompanying increased cost of equipment, chemicals, and time.

It is, therefore, the principal object of the presgenated hydrocarbons from carbon monoxide and hydrogen.

Another object of the invention is to increase the yield of oxygenated products present in the water layer resulting from the hydrocarbon synthesis product and concomitantly to decrease the quantity of oxygenated product present in the oil layer resulting from said synthesis.

v Other and further objects and advantages will appear hereinafter.

It has now been found experimentally that the addition of steam to the hot products zone- Awhile total yield of oxygenated products recovered, based on the synthesis gas converted, increased about 9%, while the yieldV of water soluble alcohols increased 40%, that of water soluble acids 30%.

The addition of steam to the hydrocarbon synthesis reaction has been previously disclosed, but in these disclosures the steam was added with the synthesis gas to the catalyst in the reaction chamber in order to modify the reaction conditions and decrease carbon formation on the catalyst. It has been found that adding steam with the synthesis gas noticeably cuts down carbon formation in the catalyst, yet this effect is accompanied, over an extended period, by a certain decrease in catalyst activity and selectivity to oxygenated products. In the case of highly active catalysts this decrease in activity can be absorbed where the paramount consideration is the prevention of catalyst carbonization. In the present invention, however, this catalyst deactivating effect is completely eliminated. In accordance with the present invention, therefore, steam is not added to the catalyst but to the products of the synthesisy substantially at syn-- thesis temperatures.

The invention has the further advantage that by its application oxygenated products are preferentially obtained in the aqueous phase than in the oil phase in the separator. It is relatively simple to recover oxygenated products from the water layer resulting from the synthesis by such processes as simple distillation, extraction, extractive distillation, and the like. It is a far more dilicult matter torecover oxygenated products from the oil layer. In practice, these products'. are not generally recovered but the oil layerV as a whole is treated with some dehydrating agent such as bauxite and the oxygenated products conl-Y verted to olefinic material for motor fuel. By this invention, therefore, the esters. which` normally` would be soluble in and' found in theoil layer'are found in their component constituents as low'` molecular weight alcohols and acids in theiwater:

layer. Y

The mechanism by which the ester formation is inhibited and the formation of alcohols and" acids favored is not too clear. The steamf may.)- have the effect of shifting the equilibrium in the direction favoring hydrolysis of esterv that, isv for-med lower down in the.- catalyst bed, though; the-decrease in ester content and` increase ofy acida andA alcohol are substantially above that predicted by mass action considerations. Another possible effect of the steamv in. increasing the oxygenated products content of the water layerY may be in decreasing-the solubility-of oxygenatedproducts in the oil layer in. favor of the. waterlayer.

Having set forth the general nature and object of the-invention the latterwill best be understood from the more detailed description hereinafter, inv which reference will be made to the accompanying. drawing whichA shows a semi-diagram.w

matic View of a system suitable to practice. aA pre-f. ferred embodiment of theinvention..

Referring now in detail to the drawingthesys-f tem illustrated therein comprises essentially a. synthesisreactor I, av product condenser I2,.and. a water phase fractionaton I9, the functions of; which are explained below.

Synthesis reactor I containsV synthesis,catalyst` ofv any suitable composition known. in. the art. of.hydrocarbonsynthesis, such asreduced oxides, ofiron or cobalt,.supported, if desired, on.carriers,. suchaskieselguhr, silica gel, ete., and containing; small. amounts from L15-10%. ofr suitable promoters. Bestv results with respect toformation of. oxygenated products are obtained. withiron catalyst promoted with alkali promoters such as potassium. carbonate. Whie the. catalyst. may

beemployed inthe form of axedbed, it.is.pre-` ferred to useA the uidized solids. technique, be,- cause of theconsiderable advantages nwith respect to temperature control and process design.

In accordance with` the preferred embodiment,Y ofthe invention, therefore, synthesis reactor Il is.A a reactor preferably inthe form of` a Vertical, cylinderY with a conical baser and with anuppeu expanded section Z and having a grid or screen. 3V, located in the lower section toelect good gans. distribution. Reactor I is charged Withainely divided alkali-promoted iron. catalystr hav-ing; a particle size ofA from about 10U-400 mesh, preferablyabout 200 mesh. The synthesis gas mixture, having a molar ratioof Hz/CO varying between` 0,5-3-r1, preferably between about 1:1 and 2:1, is introduced-intofreactor. I through line. 4- and7 flowsV upward: through grid 3. Catalyst may. bei supplied to reactor I from catalyst hopper 55 through aerated stand pipe 6. The linear velocity of: the. gases withinreacton I is keptwithin: the approximate-range ofiOilL-.Sz feet per. second, pref-, er'ably.. about 0.4.-.1.0.- foot. per:` second so.4 asate.

maintain the catalyst in the form of a dense, highly turbulent, uidized mass having a Welldened upper level 'I, and an apparent density of from about 30 to 150 pounds per cubic foot depending upon the fluidization conditions. The pressure within reactor I is kept within the approximate range of 150 to '700 p. s..i. g. preferably Within the'lmitsof from about 250'to about 450 p. s. i. g. Only a small proportion of the powdered catalyst is carried into the disengaging section 2 of the reactor above level '1, and these catalyst particles are separated from the reaction products in a conventional gas-solids separatorsuchf ascycloneg and are returned to the i catalyst zone of" reactor I through dip pipe 9.

The.x reaction: temperature is kept constant at about-500-700f F. preferably at about 600-675 F1. andsurplus heat from the exothermic reaction mayV be. withdrawn by any conventional means, such as internal or external coils (not shown).

rIlo vvprovide the ester formation inhibiting,Y step ofthe invention, a stream. of` steam at a temperature and pressure of the same'order ofy magnitude` as= that obtaining in. the disperse phase above-- upper level-Lisinjected into reactor I a shortdistanceabove levelx ly andabove tlceI catalyst inlet, through; a number of uniformly spaced distribu` tors-located inY a manifold. I0.` The injection ofsteam is preferablyy soecontrolled that the concentrationfoflacids in the Aresulting water layer is not. substantiallyless` than. about-4 5%, in order tory make'recovery.- attractive economically; in prac-- ticethis.mean sthat steamisadded inf an amount andzat-a rate aboutfequalto that at which it-is formed ini thefhydrocarbonfsynthesis reaction..

Productvaporsand gasesv are withdrawn over# head frcmreactor I and` areipassed throughline-4 I.I-Vv into4 product condenser I2F which is cooled. to; aboutroomttemperature, by any suitable cooling.-

Aagent such asfwater supplied through line I3y oxygenated: hydrocarbons'. and water, is: passed:

throughllinef IB: to vapseparator-or settler I`I where'-7 inthe-relatively light. oil phase is separated from the relativelyA heavywater phase containing most ofi' theoxygenatedproducts. The two phases, are.

separated, lthewater phase containing the oxygenated products beingfwithdrawn downwardly from settler? I'I and, passed through line lil-intoz ai fractionatingcolumn I9; where oxygenated: productsare. recover-edf in; a manner. knownI per` se: 'Ii-he: oil layer. fromseparator Hfmayalsobe. processed'.n try-recover. oxygenated products, as'by.' extraction or distillation, or it may be treatedv with; a dehydratingf agent, such as bauxite, to convertf oxygenated; products f into olenic' mate-- rials=ofhigh octane-value, allfin a manner known.-

` inthe' art.

'Ilheembodiment of the invention illustrated-byy the; drawing1 permits*Y of numerous modification. Thus inorder to providaa longer period of time for the steamztoginter'act` with the products from: the.; synthesis.. it. may: be desirable4 to4 include A a second-.reactionv chamber aboveV cyclone 8, kept atifsubstantially thesamefreaction conditions as. the disengaging zone 2. Steam for the process.

75 mayrbagenerated by; suitable.; means, from the Effect of steam on formation of esters and on water-soluble organic products Synthesis conditions:

Temperature 650 F.

Pressure 400 p. s. i. g.

Throughput 13 v/hr./w. (S. C. FJ of F. F.2/hr./lb. of catalyst) Recycle/fresh feed ratio. 2/ 1 Hz/CO fresh feed ratio-- 1/1 Superficial inlet'l velocity 0.33 fil/sec.

Catalyst Red iron oxide, KzCOs promoted,

hydrogen sintered.

[Liquid oxygenated products yield-ccJm. of converted H2 00.]

Ratio of Added Water to Product Water None l l Total Water in product, ccJm.a 132 258 Per Cent, Conversion, Hz+C v 95.1 Product Oil, calm.a 134 Water Phase: i

Alcohols l0. 1 14. 3 Carbonyl Gpds 4.0 6.8 Acids..- 10. 0 13. 1 Esters 1.1 0. 2

Total in Water Phase 25. 2 34. 4

Oil Phase:

Alr'nhn'ls 12. 6 13. 2 Carbonyl Cpds 1l. 5 12.9 cidS. 13. 7 12. 6 Est-ers 9.3 6.0

Total in Oil Phase 47. l 44. 7

Total Ol+Water Phases:

A lnnhnls 22, 7 27, Carbonyl Cpds l5. 5 19. Acids- 23. 7 25. Estere 10. 4 6.

Total Oxygenated Cpds 72. 3 79 i Standard cubic feet. 2 Fresh feed.

The above data show an increase of watersoluble alcohol yield of about 40% for the process of the invention as compared with the conventional method of operating. ThisV is accompanied by a 30% increase in water-soluble acid yield and by about a 40% decrease in undesirable ester yield. The amount of oil-phase alcohols and acids formed with and Without the steam addition step of the reaction remains relatively unaffected.

While the foregoing-description and exemplary operation have served to illustrate specific applications and results of the invention, other modifications obvious to those skilled in the art are within the scope of the invention.

What is claimed is:

1. The process of producing water soluble oxygenated hydrocarbons from carbon monoxide and hydrogen which comprises contacting a gas mixture containing carbon monoxide and hydrogen in synthesis proportions and under synthesis conditions comprising temperatures in the range of from about 500 to about 700 F. and pressures in the range of from about 150 to about 700 p. s. i. g. with a dense fluidized mass of nely divided iron containing promoted synthesis catalyst in a reaction zone, maintaining a dense fluidized bedrof catalyst in said reaction zone, maintaining a disperse catalyst phase directly above said dense phase, withdrawing a mixture of vaporous reaction products and unreacted gases from said dense phase, passing said mixture into said disperse phase, injecting steam from a source outside of said dense phase into said disperse phase, maintaining said steam substantially out of contact with the bulk of said synthesis catalyst within said reaction zone, whereby oxidation of the bulk of said catalyst by said added steam is substantially prevented, condensing said reaction products, and recovering a product relatively rich in water-soluble oxygenated hydrocarbons.

2. The process of claim 3 in which the temperature maintained lin said disperse catalyst phase is substantially the same as that maintained in said dense phase.

3. The process of claim 1 in which said steam is at substantially the same pressure and temperature as the temperature and pressure in said dense phase reaction zone.

4. The process of claim 1 in which steam is injected into said disperse catalyst phase at approximately the same rate that steam is withdrawn from the dense phase catalyst zone.

5. In the process of making synthetic hydrocarbons and oxygenated hydrocarbons from CO and H2 by passing a gasiform stream initially containing CO and H2 upwardly through a conned bed of nely divided iron-containing solid hydrocarbon synthesis catalyst under superatmospheric pressure at an elevated temperature favorable for the formation of both hydrocarbons and oxygenated hydrocarbons, the step of increasing the relative amounts of oxygenated hydrocarbons formed, comprising introducing a predetermined amount of steam into the stream of hot reaction products immediately after it emerges from said bed, said predetermined amount of steam being at substantially the same pressure and temperature as the temperature and pressure in said confined bed, maintaining said steam substantially out of contact with the bulk of said catalyst within said reaction zone,

i whereby oxidation of the bulk of said catalyst by said added steam is substantially prevented, condensing said reaction products, and recovering a product relatively rich in water soluble oxygenated hydrocarbons.

CHARLES H. WORSHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Unit Processes in Organic Synthesis, Groggins (third edition-page G20-no drawing). 

1. THE PROCESS OF PRODUCING WATER SOLUBLE OXYGENATED HYDROCARBONS FROM CARBON MONOXIDE AND HYDROGEN WHICH COMPRISES CONTACTING A GAS MIXTURE CONTAINING CARBON MONOXIDE AND HYDROGEN IN SYNTHESIS PROPORTIONS AND UNDER SYNTHESIS CONDITIONS COMPRISING TEMPERATURES IN THE RANGE OF FROM ABOUT 500* TO ABOUT 700* F. AND PRESSURES IN THE RANGE OF FROM ABOUT 150 TO ABOUT 700 P.S.I.G. WITH A DENSE FLUIDIZED MASS OF FINELY DIVIDED IRON CONTAINING PROMOTED SYNTHESIS CATALYST IN A REACTION ZONE, MAINTAINING A DENSE FLUIDIZED BED OF CATALYST IN SAID REACTION ZONE, MAINTAINING A DISPERSED CATALYST PHASE DIRECTLY ABOVE SAID DENSE PHASE, WITHDRAWING A MIXTURE OF VAPOROUS REACTION PRODUCTS AND UNREACTED GASES FROM SAID DENSE PHASE, PASSING SAID MIXTURE INTO SAID DISPERSED PHASE, INJECTING STEAM FROM A SOURCE OUTSIDE OF SAID DENSE PHASE INTO SAID DISPERSE PHASE, MAINTAINING SAID STEAM SUBSTANTIALLY OUT OF CONTACT WITH THE BULK OF SAID SYNTHESIS CATALYST WITHIN SAID REACTION ZONE, WHEREBY OXIDATION OF THE BULK OF SAID CATALYST BY SAID ADDED STEAM IS SUBSTANTIALLY PREVENTED, CONDENSING SAID REATION PRODUCTS, AND RECOVERING A PRODUCT RELATIVELY RICH IN WATER-SOLUBLE OXYGENATED HYDROCARBONS. 